A Worcester man accused of being part of an international child pornography network will be arraigned in US District Court in Boston on Monday on charges of distribution and possession of child pornography, according to court documents. Geoffrey R. Portway, 39, was arrested in July after federal agents and state troopers searched his home and seized computers that allegedly contained at least 58 images of child pornography and images of dead children, according to documents. The investigation of the child pornography ring began in 2009 after a Milford man accidentally sent a picture of an abused 18-month-old boy to federal investigators, the Globe reported in July. That man, Robert Diduca, was later sentenced to 18 years in federal prison. The investigation has led to the arrest of about 40 suspects and the identification and rescue of about 140 abused children, according to court records.